These are highly destructive; more than enough to wipe out a big city. Users of these kind of devices should have powerful launching devices at their disposal, and it is very difficult to move these units without being detected.

In terms of a terrorist attack, it is unlikely that they would use such warheads because it would be almost impossible for them to fetch a bomber or ballistic missile, necessary to deploy devices of this kind.

The potential use of strategic weapons as such could cause a nuclear winter which would make survival unlikely.